That’s all you need to know about the motivation of the durable protagonist of Sony’s “God of War” series. Yes, the Spartan warrior got tricked into murdering his wife and daughter, but he’s been rampaging across ancient Greece for five games now. Given the thousands of corpses he’s left behind, you’d think he’d have sated his thirst for vengeance.

Instead, “God of War: Ascension” (for the PlayStation 3, $59.99) brings back the old grouch for another round of bone-crunching, head-splitting mayhem. A prequel to 2005’s original “God,” the new adventure begins with Kratos chained to a rock and tormented by Furies. Once he escapes, he resumes his bloodthirsty campaign against the capricious Greek deities.

That means more of the brutal combat for which this franchise is known, with Kratos wielding his Blades of Chaos, twin knives attached to his arms with retractable chains. The game occasionally drops limited-use weapons, like clubs or javelins, in your path, but the Blades — which can be tipped with fire, ice, lighting or the “soul of Hades” — are usually enough to get the job done.

Most of the melees in “Ascension” begin with Kratos suddenly surrounded by swarms of low-level monsters that can be easily dispatched. The big lug is surprisingly graceful, and once you get into a rhythm of attacking, dodging and leaping, the combat is as smooth as ever.

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It starts feeling creaky, though, when you get to the bombastic boss battles. These typically involve beasts many times Kratos’ size, so you just have to keep hacking away until you soften them up. Then the action shifts to “quick-time events,” in which you have to press buttons to match onscreen prompts — a technique that short-circuits your rhythm and effectively takes control away from you.

The carnage is occasionally interrupted by gigantic spaces in which you have to figure out how to get Kratos to the exit. Most of these puzzle rooms are fairly trite, requiring an all-too-familiar formula of block pushing, switch pulling and wall climbing, although they get more interesting toward the end after Kratos has found some magic artifacts.

The story here is the series’ weakest yet. Six games in, the creators have pretty much used up all the cool Greek gods — Kratos has already killed Zeus, Ares, Poseidon, Hades and a few dozen more — so we’re left with third-stringers like the Scribe of Hecatonchires. And the writers don’t do themselves any favors by telling the story of “Ascension” as a series of flashbacks and flash-forwards. The result is an incoherent mess that’s probably more satisfying if you forget about the plot and just enjoy it as a series of flamboyant set pieces.

“Ascension” finally introduces online action to the franchise, so if you’ve been dying to see a bunch of Kratos-like meatheads beating on each other, you’re in luck. There are the standard multiplayer contests — deathmatch, capture-the-flag and a co-op mode in which you fight waves of increasingly powerful beasts — but they’re livened up by occasional interference by the gods themselves.

The latest “God of War” is as gory as ever. If you don’t know the meaning of “visceral,” you will after you’ve disemboweled a centaur. And it suffers from a lack of humor, treating Kratos’ travails and torments with an unwarranted degree of gravity. There’s the occasional glimpse of camp — say, when Kratos rides a giant snake through a tunnel, but even then I wasn’t sure the designers realized how ridiculous the story is. Frankly, the tormented Spartan seems more exhausted than bloodthirsty, and it’s time Sony gave him a rest. Two stars out of four.